The current big fight is between what for simplicity we can call “capitalism” and “communism.” Popular opinion would claim that communism lost. I believe that what we call capitalism may also fail, and for many of the same reasons.
We are not equal and we hate it
Despite all the happy talk, we are not all equal. Each of us has different talents and abilities; half us will be worse than average. Even when we have equal talents or abilities, circumstances can bring us very different outcomes. This can lead to resentment and hopelessness from those not gifted or lucky, and guilt and pride from those who were. The ungifted rage against the “unfair” rewards to the gifted, while the gifted feel both pride (better than you) and guilt at their gifts. Pride cause the gifted to believe their position is a sign of the inherent goodness. Guilt, perhaps, is more a feature of capitalistic societies. Guilt drives the successful to try to make amends, but self-interest means they want to do it in ways that do not harm themselves.
Rewards are not just unequal, they are very unequal
As I discussed before, whether it is wealth, power, number of fans, or blog hits, the rewards to success are not linear. The top one percent will garner vastly more than even the top ten percent. Instead of a world where the best garners slightly more than the second best, and they both garner a good bit more than the average, we have a world where the best garner huge rewards and the rest share relatively little. It does not matter what the rewards are (money, power, or sex); that skewed distribution causes problems. Under communism, it was political power; under capitalism, it is wealth; in many societies it is sex (harems). The “alpha” versus “beta” divide in the PUA world is an example of this division; the biggest players have vastly more partners than the average chump.
[I realize that all three are linked, in all societies, and that one tends to lead to the others. However, each society has a primary one. In capitalistic societies, it is earn wealth and use wealth to get power and babes. In communistic societies, it is garner power and use that power to sequester wealth and get the babes. In older societies it was get the babes (by war or careful marriages) to increase your power base, use that power base to garner wealth (perhaps by war).]
We will always end up with an elite, and they will never care about the rest.
Because of the vast differences in rewards, we will end up with an elite. That is, we will end up with a group that has vastly more resources (wealth, power, or babes) than the rest. The communists had party insiders; capitalism has corporate titans. Because they are the elite, and thus disconnected from everyone else, they will soon see the rest as “others” about whom the need not care. Indeed, they may see the “others” as a threat (or at least an inconvenience).
Resentment towards the elite
With vastly uneven rewards and an elite group that seems hostile towrds the rest, it does not take long for the rest to feel resentment towards the elite. Indeed in attempt to move things in their favor and protect their position the elites may actually break the order that brought them to their position. Eventually we have some kind of revolt that attempts to overthrow, or at least disrupt, the current system. We see this currently with the increasing hostility to, and distrust of government and corporate power.
What next? Who knows?
I do not know if the current system will collapse. If it does, I have no idea what might replace it; perhaps a more localist form of (somewhat) free markets with less global trade and fewer transnational corporations. Maybe, like the Soviet Union, we will limp along far beyond our expected end-date.